Gas turbine fuel control



Apri! 19, 1966 1. E. SMITH ETAL 3,246,470

GAS TURBINE FUEL CONTROL Filed Maron 25, 1963 2 Sheets-Sheet l April 19, 1966 J. E. SMITH ETAL 3,246,410

GAS TURBINE FUEL CONTROL Filed March 25, 1963 2 Shee'cs--SheeI 2 f7 /lg ffl/6L 70744( Ff United States Patent O 3,246,470 i GAS TURBINE FUEL CONTROL John E. Smith, Rochester, and Warren H. Cowles, Birmingham, Mich., assignors to Holley Carburetor Company, Warren, Mich., a corporation of Michigan Filed Mar. 25, 1963, Ser. No. 267,748 16 Claims. (Cl. 60-39.17)

The invention relates to fuel controls and refers more specifically to high pressure fuel metering apparatus for metering fuel to a gas turbine engine or simil-ar apparatus in response to engine compressor pressure and modulating the fuel metered to the engine in accordance with engine speed between predetermined limits at selected governing speed including means providing primary and secondary fuel, the total fuel flow being proportional to compressor discharge pressure. i

Fuel metering apparatus for turbine engines are known which meter fuel in accordance with engine speed and another engine parameter, such as compressor pressure, to maintain engine speed substantially constant at any selected speed land meter fuel in response to compressor pressure or other engine parameter only during engine acceleration and' deceleration. In this regard reference is'made to the commonly owned prior filed patent applications, Serial No. 143,880, filed October 9, 1961, now Patent No. 3,183,957, :and Serial No. 198,158, filed May 28, 1962. These prior known fuel controls are for rel-atively low pressure applications and are primarilyl for use in installations wherein a single metered fuel ow output is required.

' It is one of the objects of the present invention to provide a high pressure fuel metering control operable to meter fuel to a turbine engine or similar utilizing device in accordance with compressor pressure or similar engine parameter and to` modulate the metered fuel between predetermined limits in accordance with engine speed at any selected governing speed.

Another object is to provide a fuel metering control as set forth above wherein the metered fuel is divided in a predetermined variable ratioV between prim-ary and secondary output fuel ows, but wherein the total metered fuel is proportional to compressor discharge pressure.

Another object is to provide a fuel metering control as set forth above including a positive displacement high pressure pump.

' Another object is to provide a fuel meteringcontrol as set vforth above including la throttling valve adjustable to compensate for different fuel metered therethrough.

Another object is tol provide a fuel metering control as set forth above including electrical power turbine overspeed and pump input fuel cut-off apparatus.

' Another object is to provide a fuel metering control as set' forth above including means for limiting the horsepower of the engine with which it is used.

Another object is to provide a fuel metering control as set forth above including means for limiting the secondtary` fuel ilow in` accordance with a predetermined engine parameter.

Another object is tov provide a high pressure gas turbine fuel control which` is simple in construction, economical to manufacture and efficient in use. Y

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is a diagrammatic'representation of a fuel control constructed in accordance with the invention.

FRIGURE 2 is a block diagram of a turbine engine with which the fuel control of FIGURE 1 may be used,

3,246,470 Patented Apr. 19, 1966 ICC FIGURE 3 is a graphical representation of the metered fuel flow through the fuel control illustrated in FIG- URE 1 showing the variable ratio maintained between the secondary fuel flow and primary fuel ow and the constant ratio between total iiow and compressor discharge pressure.

With particular reference to the drawings one embodiment will now be disclosed.

In accordance with the invention the fuel control 10 illustrated in FIGURE 1 is provided to meter primary and secondary fuel to a gas turbine engine 12 shown in block diagram form in FIGURE 2 in a' predetermined variable ratio as illustrated graphically in FIGURE 3.

Theengine 12 includes three separate drive shafts 14, 16 and 18 connected respectively between 1a rst low pressure `air compressor 20 and drive turbine 22 therefor, a second high pressure air compressor 24 and drive turbine 26 therefor, and the power turbine 28 and a power utilizing device such as an airplane propeller (not shown) or the like. In the engine 12 shown in FIGURE 2 the -air flow is from the air intake through the compressor 20, a cooler 3l), second compressor 24, a heat exchanger 32, primary burner 34, turbine 26,. the seco-ndary burner 36, power turbine 28 and turbine 22 and out of the engine through the heat exchanger 32. i

As indicated in FIGURE 2 a primary fuel input is metered to the primary burner 34 through the primary fuel conduit 38 while secondary fuel is metered to the secondary burner 36 through the secondary fuel conduit 40. Pressurev P2 is transmitted from the compressor 20 to -the fuel control 10 through pressure conduit 44 for limiting the secondary fuel metered to the secondary burner as will be considered in more detail subsequently. Pressure P1 from the secondary burner input is transmitted to the fuel control 10 through pressure conduit 42 to limit the horsepower output of the engine 12, also in a manner to be more fully explained in consideration of the details of the fuel control 10.

Thus in operation of the engine 12 the air from engine air intake is first compressed in compressor 20, cooled in cooler 30, compressed again in the high pressure compressor 24, heated to a predetermined heat in the heat exchanger 32 and then is mixed with the primary fuel in the primary burner 34 in which it is ignited to produce combustion gases to operate turbine 26 which drives the high pressure compressor 24. The combustion gases from primary burner 34 after passing through turbine 26 -are passed to the secondary burner 36 where they are mixed with the secondary fue-l and ignited again to produce combustion gases to operate the power turbine 28 and turbine 22 which drives the low pressurecompressor- 20. The exhaust combustion gases from secondary burner 36 are then passed through the heat exchanger 32 and out of the engine 12.

The fuel control 10 which supplies the primary and secondary fuel to the engine 12 is positioned between a fuel tank 46 and boost pump 48 connected in ser-ies and the primary burner 34 and seconda-ry burner 36 of the engine 12 connected in parallel. In this particular embodiment of the invention, drive shaft 50 of the fuel control 16, which is rotatably mounted in sealed bearings 52, is connected to the engine 12 by convenient means (not shown) for rota-tion in accordance with the speed of turbine 26.

Turbine fuel lcontrol 10 includes the positive displacement pump 54 for continuously pumping a quantity of fuel delivered to the fuel con-trol 1t) by the boost pump 48 in excess of the requirements of the engine 12. Compu-ting mechanism 56 and governing apparatus 58 in conjunction with throttle valve assembly 59 are operable to control metering of fuel t-o the bur-ners 34 and 36 at a high pressure in accordance with the discharge pressure P3 of high pressure compressor 24 of engine 12 transmitted to the fuel control .10 through pressure conduit 61 and to modulate the metered fuel between predetermined limit-s at any selected governing engine speed.

Fuel dividing apparatus 60 is provided in the fuel control to divide the fuel metered to the engine 12 between primary and secondary fuel in accordance with a predetermined variable ratio. In .addition an electrical fuel cut-off and power turbine overspeed structure 62 and temperature compensating means 64 as well as secondary fuel limiting apparatus 65 and engine horsepower output limiting apparatus 67 are also provided in the fuel control 10.

The electrical fuel cut-off and power turbine overspeed structure 62, as shown in FIGURE 1, includes the solenoid 66 which is connected to the source of electrical energy 68 on closing of the automatic start switch 70 providing the power turbine overspeed switch 72 is closed. Solenoid 66 is operable on being energized to move the armature 74 lto the left, as shown in FIGURE 1, in opposition to lthe bias of spring 76 which tends to move the armature 74 t-o the right into closing engagement with the fuel input orifice 7 8. With either the autom-atic star-t switch 70 open or on power turbine overspeed which will open the switch 72, all fuel flow into the fuel control 10 will be cut off due to the valving portion 73 of armature 74 closing fluid input orifice '78.

The placing of the fuel cut-off and power turbine overspeed structure 62 at the input to the fuel control 10 is advantageous in fuel controls wherein the fuel output is divided into a'plurality of different fuel flows since a single relatively simple mechanism is operable to cut all fuel flow to the engine olf with such placement. A plurality of simple mechanisms or a more complicated mechanism would be required to provide fuel cut-olf at each of the plurality of output fuel flows if the fuel cutoff and power turbine overspeed structure 62 were located at the fuel output of fuel control 10 as in the past.

The positive displacement pump 54 receives the fuel at a relatively low pressure P4 at its input and is operable to boost the presure up to a relatively high output pressure P5. Pump 54 as previously indicated is of a size to always pump more fuel than is required by the engine i12 to which the fuel control 10 meters fuel. The excess fuel pumped b-y pump 54 is normally bypassed back to the pump inp-ut through the throttle valve assembly 59 as will be considered in more detail subsequently. Should the fuel pressure P5 at the output of pump 54 exceed a predetermined value the pressure relief valve 80 is provided to permit direct bypassing of the excess fuel from the output conduit 82 of the pump 54 through the conduit 84 and into the return conduit 86 back to the input of the pump 54 at the relatively low return pressure P4.

The governing apparatus 58 includes the lever 88 pivotally mounted at 90 which is provided with a valving surface 92 operable to control the valve orifice 94 in Iaccordance with the pivotal position of the lever 88. Lever 88 is movable between adjustable maximum fuel ow stop 96 and minimum fuel flow stop 98 in accordance with the forces transmitted thereto through composite member 1130 supported for movement in accordance With the force applied thereto by diaphragm 102 and the spring 106.

The force applied to lever 88 through composite member 100 due to diaphragm 102 is determined by the area of the diaphragm 102 and the pressure differential P6 in chamber 168 minus P7 in chamber 110. Pressure P6 is determined by the area of the xed orice l112 and pump pressure P5 while pressure P7 is less than pressure P6 by an amount proportional to engine speed squared.

The hydraulic speed sense 114 controls the pressure difference P6-P7 since as the shaft 50 is rotated in accordance with the speed of turbine 26, the centrifugal valve CTI member 116 is moved in accordance therewith or radially outwardly at higher engine speeds to more nearly close the valve orifice '113 and provide a greater pressure drop across the hydraulic resistor. Thus at greater engine speeds the pressure difference P6-P7 is greater than at lower engine speeds so that as engine speed increases the lever 88 tends to move clockwise under the inlluence of the pressure differential across the diaphragm 102 to perform a governing function as will be considered in more detail subsequently.

The force applied'to the lever 88 through composite member by the spring 106 is determined primarily by the position of the retaining cup 120 for the spring 106. The position of the retaining cup 120 is determined by the lever 122 which is pivotally mounted at 124 and is pivoted in accordance with the cam surface 126. Cam surface 126 is rotatable by the external fuel control lever 12S which lis positionable to determine a selected engine governing speed. The adjustable idle abutment 130 is provided in conjunction with the lever 122 to provide a minimum setting of the lever 122 suicient to permit the fuel control 10 to meter idle fuel to the engine V12.

The throttle valve assembly 59 comprises the valve orifice 134 operable to connect the chamber 110 with the low pressure return conduit 86 through conduit 136 which is maintained at the low return pressure P4. The valve orifice 134 is controlled by means of valve member 138 supported by diaphragm 140` and movable toward and away from t-he valve orifice 134 in accordance with the pressure P8 in chamber 142 and pressure P7 in charnber 110 and the bias of springs 144 and 146 acting thereon. The force of springs 144 and 146 is varied by means of the adjustable plug 14S whereby the same throttling characteristics may be maintained in the fuel control 10 for fuels having different characteristics such as density.

Computing mechanism 56 comprises the pivotally mounted lever 150, the pivotal mounting 152 of which is shown displaced at ninety degrees for clarity. The valve orifice 154 is controlled by the valving surface 156 of the lever 150. Lever is pivoted about the pivot mounting means 152 in accordance with the forces applied thereto through the rigid connection therewith of pin 15S secured to the composite member 160, the movement of which is controlled by the diaphragms 162 and 164.

Movement of the lever 150 is further controlled in accordance with the force applied to the lever extension 166 by means of the evacuated bellows 163 and the spring 170 through member 172. Lever extension 166 is rigidly secured to the lever 150 for movement therewith. Spring 170 is adjustably tensioned by means of the adjusting screw 176 and retaining cup 178 therefor. The force provided by bellows 168 is varied in accordance with compressor discharge pressure P3 and further provides a limit on the horsepower of the engine to which the fuel control 10 meters fuel as well be considered subsequently.

Fuel flow through the fuel control 10 from the pump 54 is divided between that required to sense engine speed which is removed from conduit 82 through conduit 84 and fixed orifice 112, excess pump capacity which is returned to the chamber 110 through the conduit 180 in accordance with the position` of the lever 150 and the fuel flow past the restricting orifice 134 which may be indicated was Wf|-q where Wf is the fuel metered to the engine 12 and q or governing fuel is a quantity of fuel also in excess of the required capacity pumped by the pump and which is used in governing the speed of engine 12 and which is recirculated.

Thus it will be readily recognized that the pressure difference P5-P8 which is proportional to the square of the fuel ow through the orifice 184 will be proportional to Wf2-l-2qWf-l-q2 which pressure difference is found across chamber 186 and 188 connnected to conduit 82 through conduits 192 and 194.

The governing fuel q is returned to the chamber 110 through the conduit 196.` Engine fuel Wf proceeds through the orice 198 creating a pressureV difference P8-P9 across orifice 198 which is proportional to Wf2. P9 is transmitted to chambers 200, 202 and 204 through conduits 206, 208 and 210 respectively.

Thus it will be seen that the forces acting on the lever 150 which determine the position of the valve surface 156 comprise a force proportional to WfZ-l-,ZqWf-i-q? acting downwardly and a force Wfz acting upwardly due to the enlarged diameter of diaphragm 164 as compared to the diameter of diaphragm 162. In addition it can be seen that the force of spring 170 may be set to counteract the q? force acting downwardly on the lever 150 through pin 158. Thus the force provided on the lever 150 by the bellows 168 which is proportional to the discharge pressure of compressor 24 or P3 may be equated to the force ZqWf whereby the force Wf tending to rotate the lever 150 about the pivot mounting 152 or in other words the total fuel tiow metered to lthe engine 12 will be proportional to compressor pressure when governing fuel flow q is a constant as it will be during acceleration or deceleration schedules as well be more evident when the operation of the governing apparatus 5,8 and computing mechanism 56 is considered.

In considering the over-all operation of the governing apparatus 58 and computing mechanism 56 of the fuel control 10 it will be assumed that the engine 12 is operating in a steady state condition above idle speed with the lever 128 of the governing apparatus 58 rotated so that lever 122 positions cup 120 to provide a spring force 106 acting on lever 88 which is sufficient to maintain the lever 88 some place between the maximum and minimum fuel flow abutments 96 and 98 in conjunction with the pressure differential Ps-P, across diaphragm 102. If the engine should then slow down as sensed by the speed sense 114 rotatable with shaft 50 at a speed proportional to engine speed the valve 116 would be forced inwardly by the pressure P6 acting in opposition to centrifugal force thereon whereby the pressure P6 would decrease to some value closer to P7 so that the pressure differential P-Pq would be smaller and the lever 88 would be pivoted toward the maximum fuel ow abutment 96,

Pivoting of the lever 88 toward the abutment 96 would more nearly close the valve orifice 94 to restrict the recirculated q fuel flow whereby less fuel is bypassed back to the input of pump 50 through conduit 196 and chamber 110 and more fuel is metered to the engine 12 through orifice 198 in accordance with the relation P3=V2qWf. The speed of the engine 12 will thus be brought back to the selected governing speed.

If the speed of the engine 12 is increased the lever 88 would tend to pivot clockwise about the pivot mounting 90 thereof toward abutment 98 whereby the orifice 94 would be opened to a greater degree, the recirculated portion q of the fuel ow Wf-l-q would be increased and the fuel flow Wf to the engine 12 decreased to lower the engine speed to governed speed as set by lever 1,28 again in accordance with the relation P3=2qWf wherein q is a multiplier and therefore of more signcance than q in the relation Wf-l-q equals a constant.

During such governing action the lever 150 which controls the amount of fuel pumped by pump 54 which is returned to the pump 54 through Conduit 1,50, ,Chamber 110 and throttle valve assembly 59 is also positioned in accordance with governing fuel ow q and engine fuel flow Wf as sensed across diaphragrns 162 and 164 and in accordance with engine compressor pressure P3 as sensed by evacuated bellows 168 in accordance with the above considered relation P3=2qWf.

As long as the lever 88 moves between the stops 96 and 98 the primary control of the fuel ow through the fuel control 10 is by the governing mechanism V58. However, when -it is desired to accelerate or decelerate the engine, as will be accomplished through resetting of the lever 128, the computer mechanism controls the metering of the total fuel to the engine 12 in accordance with engine compressor pressure substantially independently of the governing apparatus since lever 88 at this time will be in abutment with either the maximum fuel flow stop 96 or the minimum fuel ow stop 98. With lever 88 against stop 96 or 98 the valve orifice 94 is a constant area. The pressure drop across the constant area is maintained constant by the throttle valve assembly 59 so that governing fuel flow q will be a constant.

Therefore, during acceleration and deceleration with the diaphragrns 162 and 164 and the bellows 168 properly sized, the length of lever between mounting 152 and pin 158 and the length of lever extension 166 correctly selected, and the spring chosen to have a predetermined spring force so that the q2 force is cancelled, the fuel flow Wf will be proportional to engine compressor pressure P3 in accordance with the equation P3 is proportional to ZqWf as set forth above.

Since the spring 170 is not normally changed between acceleration and deceleration schedules it will be recognized that lthe spring 170 if it cancels out the q2 term in fthe above equation during acceleration will not completely cancel out the q2 term during deceleration since governing fuel ow q at these times will be constant Ebut different owing to the different open-ing of valve orifice 94 with the lever 88 abutting the abutments 96 and 98. Spring force 170 is therefore chosen to cancel the q2 force during for example acceleration which is the most critical condition. When q changes the proportionality between P3 and Wf changes as seen in the equation P3=2qWf. Therefore, the deceleration schedule would basically be a percentage of the acceleration schedule. This would be the precise result if the spring 170 were to change its force to constantly cancel out q2. However, the effect of not changing the force in the spring 170 would be to change the 4basic deceleration schedule by approximately a constant value.

The compressor discharge pressure P3 force is varied =by means of the temperature compensating apparatus 64 to compensate for different engine air input temperatures. Apparatus 64 may `for example sense either colmpressor inlet temperatu-re or burner inlet temperature and functions to modify the compressor discharge pressure P3 to lower the fuel flow with increases in temperature. Y

Apparatus `64 includes the vaive member 214 positioned in the pressure conduit line 216 to restrict the vent passage 218 which yvent-s condu-it 216 to atmosphere. The valve member 214 is guided by means of the hats'haped mounting bracket 220 therefor and is urged to- Ward the venting passage 218 by the spring bias means 222. The bi-metallic discs 224 operating between the end of the hat-shaped member 220 and the enlarged end 20.6 of the valve member 214 are exposed to the temperature by which it is desired to regulate the fuel ow through the openings 2128 in the shield 230 placed therearound. The air is metered into the conduit'216 through :the restriction 232 from the compressor discharge conduit 611.

A second valve member 234 is positioned in the conduit 216 downstream of the temperature compensating `apparatus 64 which valve is supported on member 236 `and diaphragm 238 and is urged toward the atmospheric exhaust passage 240 by the adjustable spring 242. The chamber 244 is exposed to atmospheric pressure While the chamber 246 is exposed to the low pressure compressor discharge pressure P2. Thus in operation the horsepower output of the engine 12 may be effectively limited by varying the pressure P10 acting on bellows 1,68 in accordance with the low pressure compressor discharge pressure P2. The horsepower limit may be established by position-ing of the plug 248.

Fuel flow Wr passing through the restriction -198 is divided into primary and secondary fuel flow as previ,-

ously indicated. Thus primary fuel flow is provided through condui-t 208, valve orifice 250, past cut-off valve 252 and into primary fuel conduit 38 in accordance with pressure difference PB-Pg across the diaphragm 254. The pressure difference Pfg-P9 across diaphragm 254 positions valve 256 with respect Ito the valve orifice 254) in opposition to the bias spring 258.

In other words since the computer mechanism 56 has meter fuel flow Wf to the orifice 198, and since this orifice is fixed in area, the pressure drop P2439 provides an indication at the diaphragm 164 of the computer mechanism 56 that the metered amount of fuel is correct. The pressure drop PBQPQ can thus be used as an indication of total fuel flow.

The position of valve 256 provides a pressure difference P9 to P11 across the valve orifice 250 so that the pressures acting on the diaphragm 260 and valve member 262 which regulate the secondary fuel metering ori- 'fico 264 varies in accordance with pressure difference PVPH. The pressure difference P9-P11 in opposition to bias Ispring 266 positions the valve 262 with respect to the orifice 264 so that the secondary fuel flow provides a pressure difference 13g-P12 yacross the orifice 264 and a secondary fuel flow in conduit 40 which is the difference between the fuel flow Wf through orifice 198 and the primary fuel flow through valve orifice 250.

The cut-off valve 252 is provided in conjunction with `the cam 268 to positively shut off the primary fuel when the cam 268 which may be mechanically connected to the lever 128 is rotated to cause movement of the valve 252 to its rightwa-rd limiting position. The valve 2.52 is normally urged by spring 27th toward its rightwardmost position whereby cut-off valve 25.2 also acts as a pressurizing valve for the fuel control 10. This insures that the pump pressure rise is never less than a predetermined quantity related to the force of spring lflwhereby a pressure differential sufficient 'to opera-te all hydraulic circuits and to permit bypassing fuel flow in control 1i! is maintained at all times.

Secondary fuel may be bypassed to the low pressure return conduit 86 through conduits 12712 and 27-4 on movement of the valve 276 to the right from the position thereof shown in FIGUR'E 1. yValve 276 is supported for movement in passage 278 by diaphragm 280 and member 282. Diaphragm 280 and member 282 are urged to the left by spring 284 and to the right by the pres-sure P1 which is ltransmitted thereto from the high pressure compressor turbine 26 through conduit 42. Bypassing of the secondary fuel back to the pump input effectively limits the power turbine output .to prevent power turbine overs-peed. The speed at which the power `turbine is limited is adjustable by means of the adjusting plug 288.

The drawings and the foregoing specification consti- 'tute a description of the improved fuel control in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims,

Wha-t we claim as our invention is:

1. A fuel control for metering fuel from a fuel source to a turbine engine comprising -a fuel conduit extending between the fuel source and turbine engine, a first and second fixed restriction in said fuel conduit, a pump operably associated with said conduit for pumping fuel from said fuel source into said conduit always in excess of the fuel requirements of said engine, a pressure regulating check valve connected in parallel with said pump vfor bypassing fuel from the output to the input thereof a a throttle valve, engine compressor pressure responsive computing mechanism operably associated with said throttle valve and connected to said conduit between the pump and first restriction for returning a portion of the fuel in excess of engine requirements to the input side of said pump, governing apparatus connected to said conduit between said first and second restrictions and operably associated with said computing mechanism and throttle valve for modulating the fuel passing through the second restriction in accordance with engine speed and means connected to the conduit between the second restriction and engine responsive to the pressure drop across the second restriction for dividing the fuel into primary and secondary engine fuel in a predetermined variable proportion.

2. Structure as set forth in claim 1 wherein the computing mechanism includes a valve orifice through which fuel is returned to the input side of said pump, a lever pivotally mounted centrally having a valve surface on one end thereof positioned adjacent the valve orifice for varying the opening of the valve orifice to regulate the quantity of fuel returned to the input side of the pump in accordance with the pivotal position of the lever and pressure responsive means engaged with the other end of the lever responsive to engine compressor pressure for pivoting the lever in accordance with engine compressor pressure.

3. Structure as set forth in claim 2 wherein the computing mechanism further includes a pair of spaced apart diaphragms defining three separate chambers within the fuel control, means for connecting the first of said chambers to the fuel conduit between the pump and first restrictie-n, means for connecting the second of said chambers to the fuel conduit between the second restriction and engine, and means for connecting the third of said chambers to the fuel conduit between the first and second restriction, means connecting the diagrams for movement together and means connecting said diaphragms to said lever to produce movement thereof in accordance with the movement of said diaphragms.

4. Structure as claimed in claim 1 wherein one governing apparatus includes a valving orifice through which fuel in said fuel conduit is metered for return to the pump input to modulate the fuel metered to the engine, a lever pivotally mounted at one end having a valving surface thereon operable to vary the orifice in accordance with the pivotal position of said lever, a pair of stops on opposite sides of the other end of said lever, resilient means for biasing said lever toward one of said stops operable to establish a predetermined governing speed, diaphragm means, a hydraulic speed sense for creating `a pressure differential across Said rdiaphragm means in accordance with engine speed, and means connected to said diaphragm means engageable with said lever operable to pivot said lever between said stops in opposition to said relisient means in accordance with the pressure differential across the diaphragm means.

5. Structure as Set forth in claim 4 wherein said throttle valve comprises a valve orifice through which fuel is metered back to the input side of the pump, a diaphragm mounted valve member operable to regulate the valve orifice, settable resilient means biasing said valve member in a predetermined direc-tion and means for applying the pressure differential between the output pressure of the speed sense and the pressure in the fuel conduit between the first and second restrictions across the diaphragm mounted valve member.

6. Structure as set forth in claim 1 wherein the means for dividing the fuel metered through said second fixed restriction comprises .a first diaphragm, a valve member located in the fuel conduit between the second restriction and engine and secured to said first diaphragm for movement therewith, means for connecting one side of said first diaphragm to the fuel conduit between the first and second restrictions, means for connecting the other side of the first diaphragm to the fuel conduit between the second fixed restriction and the valve whereby the valve member is positioned in accordance with the pressure drop across the second restriction to provide a primary fuel flow therethrough and produce a pressure drop thereacross, a second diaphragm mounted valve in said fuel conduit controlling the flow of secondary fuel, and means for applying the pressure drop across said first valve to said second valve to determine the amount of secondary fuel fiow through said second valve.

7.v Structure as set forth in claim 6 and further including means for limiting the portion of secondary fuel flow delivered to the engine in accordance with a predetermined engine parameter.

8. A fuel control for metering fuel from a fuel source to a turbine engine comprising a fuel conduit extending between the fuel source and turbine engine, a first and second fixed restriction in said fuel condui-t, a pump operably associated with said conduit for pumping fuel from said fuel source into said conduit always in excess of the fuel requirements of said engine, a pressure regulating check valv-e connected in parallel with s-aid pump for bypassing fuel from the output to the input thereof, a throttle valve, engine compressor pressure responsive computing mechanism operably associated with said throttle valve and connected to said conduit between the pump and rst restriction for returning a portion o-f the fuel in excess of engine requirements to the input side of said pump, and governing apparatus connected to said conduit between said first and second restrictions and operably associated with said computing mechanism and throttle valve for modulating the fuel passing through the second restriction in accordance with engine speed.

9. Structure as set forth in 4claim 8 wherein the computing mechanism includes a valve orifice through which fuel is returned to the input side of said pump, a lever pivotally mounted centrally having a valve surface o-n one end thereof positioned adjacent the valve orifice for varying the opening of the valve o-rifice to regulate the quantity of fuel returned to the input side of the pump in accordanme with the pivotal position of the lever and pressure responsive means engaged with the other end of the lever responsive to engine `compressor pressure for pivoting lthe lever in accordance with engine compressor pre-ssure.

10. Structure as set forth in claim 9 wherein the cornputing mechanism further inclu-des a pair of spaced apart diaphragms defining three separate chambers Within the fuel control, means for connecting the first of said chambers to the fuel conduit between the pump and first restriction, means for connecting the second of said chambers to the fuel conduit between the second restriction and engine, and means for connecting the third of said chambers to the fuel conduit between the first and second restriction, means connecting the diaphragms for movement together and means connecting said diaphragms to said lever to produce movement thereof in accordance with the movement of said diaphragms.

11. Structure as claimed in claim 8 wherein the governing apparatus includes a valving orifice through which fuel in said fuel conduit is metered for return to the pump input to modulate the fuel metered to the engine, a lever pivotally mounted at one end having a valving surface thereon operable to vary the orifice in accordance with the pivotal position of said lever, a pair of stops on opposite sides of the other end of said lever, resilient means for biasing said lever toward one of said stops operable to establish a predetermined governing speed, diaphragm means, a hydraulic speed sense for creating a pressure differential across said diaphragm means in accordance with engine speed, and means connected to said diaphragm means engageable with said lever operable to pivot said lever between said stops in opposition to said resilient means in accordance with the pressure differential across the diaphragm means.

12. Structure as set forth in claim 11 wherein said throttle valve comprises a valve orifice through which fuel is metered 4back to the input side of the pump, a diaphragm mounted valve member operable to regulate the valve orifice, settable resilient means biasing said valve member in a predetermined direction and means for applying the pressure differential between the output l@ pressure of the speed sense and the pressure in the fuel conduit between the first and second restrictions across the diaphragm mounted valve member.

f3. A fuel control for metering fuel from a fuel source to a turbine engine which engine includes a high pressure compressor, a high pressure compressor turbine driving the high pressure compressor, a primary fuel burner positioned between the high pressure compressor and the high pressure compressor turbine, a power turbine and a secondary fuel burner positioned between the high pressure compressor turbine and the power turbine, said fuel control comprising a fuel conduit extending between the fuel source and the turbine engine, a first yand second fixed restriction in said fuel con-duit, a pump for pumping fuel from said fuel source into said conduit always in excess of the fuel requirements of said engine, a throttle valve, engine compressor pressure responsive computing mechanism operably associated with said throttle valve and connected to said conduit between the pump and iirst restriction for returning a portion of the fuel in excess of engine requirements to the input side of said pump including a valve orifice through which fuel is returned to the input side of said pump, a lever pivotally mounted ccntrally having a valve surface on one end there-of positioned adjacent the valve orice for varying the opening of the valve orifice to regulate the quantity of fuel returned to the input side of the pump in accordance with the pivotal position of the lever, pressure responsive means engaged with the other end of the lever responsive to engine compressor pressure for pivoting the lever in accordance with engine compressor pressure, a pair of spaced apart diaghragms defining three separate chambers within the fuel control means for connecting the first of said chambers to the fuel conduit between the pump and first restriction, means for connecting the second of said chambers to the fuel conduit between the second restriction and engine and means for connecting the third of said chambers to the fuel conduit between the first Aand second restrictions, means connecting the diaphragms for movement together and means connecting said diaphragms to said lever to produce movement thereof, in accordance with the movement of said diaphragms, governing apparatus connected to said conduit between said first and second restrictions and operably associated with said computing mechanism and throttle valve for modulating the fuel passing through the second restriction in accordance with engine speed, and means connected to the conduit between the second restriction and engine responsive to the pressure drop across the second restriction for dividing the fuel into primary and secondary engine fuel in a predetermined variable proportion and means for passing the primary fuel to the primary burner of the engine and the secondary fuel to the secondary burner of the engine.

f4. A fuel control for metering fuel from a fuel source to a turbine engine which engine includes a high pressure compressor, a high pressure compressor turbine driving the high pressure compressor, a primary fuel burner positioned between the high pressure compressor and the high pressure compressor turbine, a power turbine and a secondary fuel burner positioned between the high pressure compressor turbine and the power turbine, said fuel control comprising a fuel conduit extending between the fuel source and the turbine engine, a first and second xed restriction in said fuel conduit, a pump for pumping fuel from said fuel source into said conduit always in excess of the fuel requirements of said engine, a throttle valve, engine compressor pressure responsive computing mechanism operably associated with said throttle valve and connected to said conduit between the pump and first restriction for returning a portion of the fuel in excess of engine requirements to the input side of said pump, governing apparatus connected to said conduit between said first and second restrictions and operably associated with said computing mechanism and throttie valve for modulating the fuel passing through the second restriction in accordance with engine speed, including a valve orifice through which fuel in said fuel conduit is metered for return to the pump input to modulate the fuel metered to the engine, a lever pivotally mounted at one end having a valving surface thereon operable to vary the orifice in accordance with the pivotal position of said lever, a pair of stops on opposite sides of the other end of said lever, resilient means for biasing said lever toward one of said stops operable to establish a predetermined governing speed, diaphragm means, la hydraulic speed sense for creating a pressure differential across said diaphragm means in accordance with engine speed, and means connected to said diaphragm means engageable with said lever operable to pivot said lever between said stops in opposition to said resilient means in accordance with the pressure differential across the diaphragm means, and means connected to the conduit between the second restriction and engine responsive to the pressure drop across the second restriction for dividing the fuel into primary and secondary engine fuel in a predetermined var* iable proportion and means for passing the primary fuel to the primary burner of the engine and the secondary fuel to the secondary burner of the engine.

15. Structure as set forth in claim 14 wherein said throttle valve comprises a valve orice through which fuel is metered back to the input side of the pump, a diaphragm mounted valve member operable to regulate the valve orifice, settable resilient means biasing said valve member in a predetermined direction and means for applying the pressure differential between the output pressure of the speed sense and the pressure in the fuel conduit between the first yand lsecond restrictions across the diaphragms mounted valve member.

16. A fuel control for metering fuel from a fuel source to a turbine engine which engine includes a high pressure compressor, a high pressure compressor turbine driving the high pressure compressor, a primary fuel burner positioned between the high pressure compressor and the high pressure compressor turbine, a power turbine and a secondary fuel burner positioned between the high pressure compressor turbine `and the power turbine, said fuel control comprising a fuel conduit extending between the fuel source land the turbine engine, a rst and second fixed restriction in said fuel conduit, a pump for pumping fuel from said fuel source into said conduit always in excess of the fuel requirements of said engine, a throttle valve, engine compressor pressure responsive computing mechanism operably associated with said throttle valve and connected to said conduit between the pump and rst restriction for returning a portion of the fuel in excess of engine requirements to the input side of said pump, governing apparatus connected to said conduit between said first and second restrictions and operably associated with said computing mechanism and throttle valve for modulating the fuel passing through the second restriction in accordance with engine speed, and means connected to the conduit between the second restriction and engine responsive to the pressure drop across the second restriction for dividing the fuel into primary and secondary engine fuel in a predetermined variable proportion and means for passing the primary fuel to the primary burner of the engine and the secondary fuel to the secondary burner of the engine.

References Cited by the Examiner UNlTED STATES PATENTS 2,452,088 10/ 1948 Whitehead 137-26 2,605,610 8/ 1952 Hermitte et al. 2,667,743 2/1954 Lee 60-39.28 2,668,416 2/1954 Lee (S0-39.28 2,691,268 10/1954 Prentiss 60-39.28 2,765,800 10/1956 Drake 137-26 2,848,870 8/1958 Eastman 60-39.28 2,910,125 10/1959 Best 6039.28 2,916,876 12/1959 Colley 60-3928 2,943,447 7/ 1960 Davies 60-3928 2,947,141 8/1960 Russ 60-39.28 2,996,883 8/1961 Fortmann 60-3928 3,002,348 10/1961 Haase 60-39.28 3,041,826 7/ 1962 Coar. 3,067,580 12/1962 Kast 6039.28 3,073,115 1/1963 Cowles 60-39.28 3,104,524 9/1963 Flanders 60-39.16 3,118,491 1/ 1964 Simons 60-39.28 3,123,089 3/1964 Thrap 137-101 3,125,110 3/1964 Allen 137-101 3,131,750 5/1964 Turner 60-39.28 X 3,142,259 7/1964 Tyler 60-39.28 X

FOREIGN PATENTS 620,983 4/ 1949 Great Britain.

710,261 6/ 1954 Great Britain.

800,394 8/ 1958 Great Britain.

JULIUS E. WEST, Primary Examiner.

SAMUEL LEVINE, MARK NEWMAN, Examiners. 

1. A FUEL CONTROL FOR METERING FUEL FROM A FUEL SOURCE TO A TURBINE ENGINE COMPRISING A FUEL CONDUIT EXTENDING BETWEEN THE FUEL SOURCE AND TURBINE ENGINE, A FIRST AND SECOND FIXED RESTRICTION IN SAID FUEL CONDUIT, A PUMP OPERABLY ASSOCIATED WITH SAID CONDUIT FOR PUMPING FUEL FROM SAID FUEL SOURCE INTO SAID CONDUIT ALWAYS IN EXCESS OF THE FUEL REQUIREMENTS OF SAID ENGINE, A PRESSURE REGULATING CHECK VALVE CONNECTED IN PARALLEL WITH SAID PUMP FOR BYPASSING FUEL FROM THE OUTPUT TO THE INPUT THEREOF A A THROTTLE VALVE, ENGINE COMPRESSOR PRESSURE RESPONSIVE COMPUTING MECHANISM OPERABLY ASSOCIATED WITH SAID THROTTLE VALVE AND CONNECTED TO SAID CONDUIT BETWEEN THE PUMP AND FIRST RESTRICTION FOR RETURNING A PORTION OF THE FUEL IN EXCESS OF ENGINE REQUIREMENTS TO THE INPUT SIDE OF SAID PUMP, GOVERNING APPARATUS CONNECTED TO SAID CONDUIT BETWEEN SAID FIRST AND SECOND RESTRICTIONS AND OPERABLY ASSOCIATED WITH SAID COMPUTING MECHANISM AND THROTTLE VALVE FOR MODULATING THE FUEL PASSING THROUGH THE SECOND RESTRICTION IN ACCORDANCE WITH ENGINE SPEED AND MEANS CONNECTED TO THE CONDUIT BETWEEN THE SECOND RESTRICTION AND ENGINE RESPONSIVE TO THE PRESSURE DROP ACROSS THE SECOND RESTRICTION FOR DIVIDING THE FUEL INTO PRIMARY AND SECONDARY ENGINE FUEL IN A PREDETERMINED VARIABLE PROPORTION. 